The greasy sweat that occasionally forms between the buttocks when one is working a long shift, or hiking on a hot day. Sometimes aggrevated by a hangover or a shoddy ass wiping. Can lead to monkey butt.

I drank too much vodka the night before I had to work a double at the restaurant. My voodoo butter gave me a terrible itch!

That construction worker is so sexy, I would spread his voodoo butter on a cracker!